AESIMC—Perform the AES InvMixColumn Transformation

Opcode/Instruction	Op/En	64/32-bit Mode	CPUID Feature Flag	Description
66 0F 38 DB /r AESIMC xmm1, xmm2/m128	RM	V/V	AES	Perform the InvMixColumn transformation on a 128-bit round key from xmm2/m128 and store the result in xmm1.
VEX.128.66.0F38.WIG DB /r VAESIMC xmm1, xmm2/m128	RM	V/V	Both AES and AVX flags	Perform the InvMixColumn transformation on a 128-bit round key from xmm2/m128 and store the result in xmm1.

Instruction Operand Encoding

Op/En	Operand 1	Operand2	Operand3	Operand4
RM	ModRM:reg (w)	ModRM:r/m (r)	NA	NA

Description

Perform the InvMixColumns transformation on the source operand and store the result in the destination operand. The destination operand is an XMM register. The source operand can be an XMM register or a 128-bit memory loca-tion.

Note: the AESIMC instruction should be applied to the expanded AES round keys (except for the first and last round key) in order to prepare them for decryption using the “Equivalent Inverse Cipher” (defined in FIPS 197).

128-bit Legacy SSE version: Bits (VLMAX-1:128) of the corresponding YMM destination register remain unchanged.

VEX.128 encoded version: Bits (VLMAX-1:128) of the destination YMM register are zeroed.

Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b, otherwise instructions will #UD.

Operation

AESIMC

DEST[127:0] ← InvMixColumns( SRC );
DEST[VLMAX-1:128] (Unmodified)

VAESIMC

DEST[127:0] (cid:197) InvMixColumns( SRC );
DEST[VLMAX-1:128] (cid:197) 0;

Intel C/C++ Compiler Intrinsic Equivalent

(V)AESIMC:

__m128i _mm_aesimc (__m128i)

SIMD Floating-Point Exceptions

None

Other Exceptions

See Exceptions Type 4; additionally

#UD	If VEX.vvvv ≠ 1111B.